Chromatography columns provide a means for separating, purifying and isolating chemical and biological compounds. The size and type of column used in these operations typically depends upon the scale of the process in question, small glass or plastic walled columns typically being used for research purposes, while larger metal columns are employed for industrial processes. For instance, chromatography columns may be used in manufacturing processes to purify process liquids and separate substances of interest from such liquids; typical examples include large-scale preparative purification of fine chemicals and pharmaceuticals, together with biological products.
Whilst the present invention relates to both plastic walled and larger metal walled chromatography columns, it is particularly useful for manufacturing and industrial-scale chromatography columns. Industrial-scale chromatography columns typically comprise a hollow, axially vertical tubular housing including a liquid inlet at the upper end and through which the buffer and substances to be separated are dispensed to the media bed located within the cavity of the tube, and a liquid collecting system at the lower end for collecting substances and buffer. The particulate chromatographic media or bed through which the buffer fluid and/or substances to be separated and purified percolates is located between the liquid inlet and collecting system.
An adapter assembly is typically affixed to the upper end of the tubular housing and a base assembly to the lower end where it is bolted to the bottom flanges. Each of these assemblies typically comprises a strong backing plate and a distributor plate which further supports a bed support; a bed support is a layer of mesh, screen, filter, sinter or other fluid-permeable media-retaining material which permits process liquid flow into and out of the chromatography bed space or cavity while retaining the bed of particulate medium. To provide adjustability and control of the bed height and bed compression, the adapter assembly is typically made in the form of a piston or sliding adapter in the column tube interior. After the column is charged with bed media, typically through a valve or nozzle, the adapter may be forced toward the bottom of the tube to compress or pressurize the media bed. Generally the base assembly is a fixed structure which is bolted against the bottom flange of the column tube but, in some instances, may also be in the form of a movably slidable piston or adapter.
The backing plate of the base assembly generally acts as a support for the column, being itself supported on legs or some other stand arrangement, which allows clearance for outlet pipework projecting beneath the base assembly.
Liquid chromatography is a technique for separating the individual compounds that exist in a sample. In employing the technique, the sample is dissolved and carried in a liquid, called a mobile phase. The mobile phase carrying the sample is forced to migrate through a bed of particulate media, sometimes called a stationary phase. Different compounds will have differing rates of migration through the media, which effects the separation of the components in the sample. The bed of particulate media is formed under gravity, washing with a mobile phase, and/or by compression by an adapter or piston. Before a column can be used to separate compounds by liquid chromatography it is necessary to remove air from the bed space which has become trapped in the column otherwise the air will interfere with the separation process. The air may have been originally present in the bed space itself or have moved into the bed space from associated tubing, pumps or column components such as a bed support. Problems are often encountered in trying to remove the air from the column prior to conducting liquid chromatography. The trapped air may create air pockets in the stationary phase where chemical interaction between the sample and the media cannot take place. These air pockets thus negatively affect the separation of the different components in the sample.